Magnetic pulse welding method and apparatus for sealing a vessel and a sealed vessel

ABSTRACT

A method and a welding induction coil for sealing a vessel are provided. The method includes providing a vessel&#39;s body having an open end a cover including a welding part and a brim part. A diameter of the cover at the welding part is less than the inner diameter of the vessel&#39;s body for providing an air gap between the vessel&#39;s body and the welding part. The cover is placed within said open end of the vessel&#39;s body. A welding induction coil is provided around the vessel&#39;s body at the place where the welding part of the cover is located. The welding induction coil is energized to generate a pulsed magnetic force sufficient to cause bending a portion of the vessel&#39;s body in a radially inward direction around the cover in the air gap. The pulsed magnetic force has such a value so to provide mutual diffusion of atoms of the vessel&#39;s body and the cover at their impact, thereby to weld the vessel&#39;s body and the cover to each other.

FIELD OF THE INVENTION

This invention relates to a method and apparatus for sealing containersand in particular, for sealing vessels by a pulsed magnetic force (PMF).

BACKGROUND OF THE INVENTION

A vessel such as a container, canister, tank, flask, etc. used, forexample, for gas and/or liquid storage is usually produced bymanufacturing a vessel body portion and a cover portion separately. Forsealing the vessel, welding or crimping methods can be used for couplingthe cover portion to the vessel body portion. Welding hereinafter refersto a process in which two opposite surfaces of first and secondworkpieces form a physical joint, thereby become integrated with oneanother owing to mutual diffusion of their atoms. In turn, crimpingrefers to such joining of two workpieces, when a surface of at least oneof the workpieces becomes wavy, bent, or pinched so as to provide a“pure” mechanical joint between the two workpieces withoutinterpenetration of the atoms of the first workpiece into the body ofthe second workpiece.

The crimping is usually made by stamping or rolling. However, variouscrimping techniques are also known in the art which utilize the forcegenerated by a transient magnetic field for sealing vessels.

For example, U.S. Pat. No. 3,581,456 to Gere describes a method forforming a closure on the neck finish of a filled container whichutilizes the force generated by a transient magnetic field. The skirt ofa cap, positioned on the neck of the container, is urged by the fieldagainst the neck finish so as to cause the skirt to conform to thecontours of the neck finish and to thereby hold the cap in engagementwith the neck finish upon the neck of the container.

U.S. Pat. No. 3,957,005 describes a method for making a metal can endthat includes a body portion of substantially uniform metal thicknessand a peripheral flange of reduced metal thickness. The can end isformed from relatively thin sheet material, such as aluminum sheet orthe like, by punching or shearing a blank or disc from the sheet andforming the disc into a cup which is subjected to an ironing operationto reduce the thickness of the peripheral portion thereof and increaseits projecting length. The ironed cup is then subjected to mechanicalpressing, or magnetic discharge forming, to shape the peripheral portioninto a curvilinear flange which is adapted to be double seamed to thecan body.

U.S. Pat. No. 4,934,552 to Koide et al. describes a method for producinga sealed vessel including a cylindrical body portion having an open end,and a cover fitting in the open end of the body portion. The sealedvessel is produced by pressing the open end of the body portion from theoutside of the body portion to an outer peripheral surface of the coverprovided with at least one of annular grooves around the outerperipheral surface of the cover. In the case of using an electromagneticforce as the means for press-working, a part of the body portion isstrictly and air-tightly fixed to the annular grooves in a moment andthus the sealed vessel is produced.

U.S. Pat. No. 5,191,775 to Shiina et al. describes a technique forsealing a refrigerating-medium storage vessel which comprises a tubularbody having a bottom and an open upper end portion, and a closure fittedin the open end portion. The open end portion is constricted and crimpedby electromagnetic forming and is thereby secured to the closure bybeading and matching groove. U.S. Pat. No. 5,191,775 states that themethod does not employ welding for joining the closure to the body.

U.S. Pat. No. 5,671,522 to Aronne describes another crimping techniquefor sealing a container by magnetic pulse forming techniques. Thecontainer is closed by means of a pair of specially constructed end capseach having annular recesses formed around their circumference. The endsof the container are engaged within the recess and joined by magneticpulse forming. The magnetic pulse force is asserted radially inwardagainst a mandrel which mates with a depression formed in the caps.

The conventional welding is usually carried out by a gas weldingapparatus, laser or any other conventional welding technique. It isknown in the art that the gas welding techniques suffer from differentdisadvantages, e.g., the vessel body must be made of a heatproofmaterial, etc.

It is known in the art (see, for example, U.S. Pat. No. 5,824,998 to theAssignee of this application) that pulsed magnetic forming techniquescan also be used for cold welding two metal workpieces.

SUMMARY OF THE INVENTION

Despite the prior art in the area of sealing containers by magneticpulse forming techniques, there is still a need in the art for, and itwould be useful to have, a novel method and apparatus for sealingvessels by utilizing magnetic pulse force (PMF). It would beadvantageous to facilitate joining a vessel body and a cover by coldwelding providing mutual diffusion of their atoms.

Thus, according to one broad aspect of the invention there is provided amethod of sealing a vessel, comprising:

(a) providing a vessel's body having at least one open end;

(b) providing a cover having a welding part, where said welding part hasa diameter less than the inner diameter of the vessel's body;

(c) placing the cover within said at least one open end of the vessel'sbody, thereby an air gap is formed between said vessel's body and thewelding part of said cover;

(d) providing a welding induction coil around said vessel's body at theplace where the welding part of the cover is located; and

(e) energizing said welding induction coil to generate a pulsed magneticforce sufficient to cause bending a portion of the vessel's body in aradially inward direction around the cover in said air gap, said pulsedmagnetic force has such a value so to provide mutual diffusion of atomsof the vessel's body and the cover at their impact, thereby welding saidvessel's body and the cover to each other.

According to another broad aspect of the present invention, there isprovided a sealed vessel comprising:

a vessel's body, where said vessel's body had at least one open endbefore the vessel was sealed;

a cover having a welding part, where said welding part has a diameterless than the inner diameter of the vessel's body, thereby an air gapwas provided between said vessel's body and the welding part of saidcover placed within the said at least one open end of the vessel's bodybefore the vessel was sealed,

wherein said cover being welded to the vessel's body by a pulsedmagnetic force causing bending a portion of the vessel's body in aradially inward direction around the cover in said air gap, said pulsedmagnetic force has such a value so to provide mutual diffusion of atomsof the vessels body and the cover at their impact.

When require, the cover can include also a brim part, where a value of adiameter of the cover at the brim part is about the value of an innerdiameter of the vessel's body, thereby to provide holding the coverwithin the vessel's body.

According to yet another broad aspect of the present invention, there isprovided a welding induction coil comprising at least a one-turn coilhaving two electrodes configured for applying pulsed high voltagethereacross,

wherein said welding induction coil is configured for use with anapparatus for sealing a vessel having:

-   -   wherein said welding induction coil is configured for use with        an apparatus for sealing a vessel including:        -   a vessel's body having at least one open end, and        -   a cover having a welding part, where said welding part has a            diameter less than the inner diameter of the vessel's body,            thereby providing an air gap between said vessel's body and            the welding part of said cover when the cover is placed            within said at least one open end of the vessel's body;

wherein said welding induction coil is capable to generate a pulsedmagnetic force causing bending a portion of the vessel's body, placedwithin a working zone of said welding induction coil, in a radiallyinward direction around the cover in said air gap, said pulsed magneticforce has such a value so to provide mutual diffusion of atoms of thevessel's body and the cover at their impact, and thereby to weld saidcover to the vessel's body.

There has thus been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thereofthat follows hereinafter may be better understood. Additional detailsand advantages of the invention will be set forth in the detaileddescription, and in part will be appreciated from the description, ormay be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, a preferred embodiment will now be described, by way ofnon-limiting example only, with reference to the accompanying drawings,in which:

FIG. 1A and FIG. 1B illustrate an exploded view and a cross-sectionalview of a vessel before a sealing process, according to one embodimentof the invention;

FIGS. 2A-2D illustrate a sequence of stages of the welding process,according to an embodiment of the invention;

FIG. 3A and FIG. 3B illustrate exemplary images obtained from theexamination under an optic microscope of an etched interfacecross-section of the joint between a vessel's welding portion and acover's welding part made of low carbon steel and aluminum,respectively;

FIG. 4A and FIG. 4B illustrate an exploded view and a cross-sectionalview of the vessel before a welding process, correspondingly, accordingto another embodiment of the invention;

FIG. 5 illustrates a cross-sectional view of the vessel before a weldingprocess, according to a further embodiment of the invention;

FIG. 6 illustrates a cross-sectional view of the vessel before a weldingprocess, according to yet another embodiment of the invention;

FIGS. 7A-7C illustrate cross-sectional views of the vessel before awelding process, according to a still further embodiments of theinvention; and

FIG. 8A and FIG. 8B illustrate a prospective view and a cross-sectionalview of the welding induction coil, correspondingly, according to anembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The principles and operation of a method and an apparatus according tothe present invention may be better understood with reference to thedrawings and the accompanying description, it being understood thatthese drawings are given for illustrative purposes only and are notmeant to be limiting. The same reference numerals will be utilized foridentifying those components which are common in the vessel and theworking coil shown in the drawings throughout the present description ofthe invention. Dimensions of vessel, thickness of the walls of thevessel and cover as well as gaps between the vessel and cover and theirportions may be exaggerated for clarity.

Referring to FIG. 1A and FIG. 1B, an exploded view and a cross-sectionalview of a vessel 10 before a welding process are illustrated,correspondingly, according to one embodiment of the invention. Thevessel 10 includes a cylindrical vessel's body 11 having an open end 12and a cover 13. The cover 13 has a welding part 14 and a brim part 15.The purpose of the brim part 15 is to hold the cover 13 inside thevessel's body 11. Therefore, a diameter of the cover 13 at the brim part15 is equal to the inner diameter of the vessel's body 11. A diameter ofthe cover 13 at the welding part 14 is less than the inner diameter ofthe vessel's body. Thus, an annular air gap 16 is provided between avessel's welding portion 19 and a surface 17 of the cover's welding part14, when the cover 13 is placed into the open end 12 of the vessel'sbody 11.

The vessel 10 may be constructed of any suitable metal material havingthe required strength and forming characteristics for the particularapplication. It should be appreciated that the vessel's body 11 and thecover 13 can be made of the same material or different materials.Examples of the metal materials from which the vessel's body 11 and thecover 13 are made include, but are not limited to, aluminum, low carbonsteel, brass, copper. It should be appreciated that alloys of these andother materials can also be used.

In order to provide a force required to weld the cover 13 to thevessel's body 11, a high power pulsed magnetic field is generated aroundthe vessel's body 11 at the place where the cover's welding part 14 islocated inside the vessel's body 11. A device suitable for providing arequired magnetic pulsed magnetic field is known per se, and thereforeits construction and operation will not be expounded herebelow. Forexample, the device described in U.S. Pat. No. 5,824,998 to the Assigneeof this application, incorporated herein by reference, can be used forthe purpose of the present invention. Such a device includes a weldinginduction coil, which can be configured in accordance with a specificapplication. In FIG. 1B the welding induction coil surrounds thevessel's body 11 and is indicated by a reference numeral 18. An exampleof the configuration of the welding induction coil 18 suitable for thepresent invention will be described in detail hereinbelow.

Referring to FIGS. 2A-2D, a sequence of stages of the welding process isillustrated, according to an embodiment of the invention. It should benoted that these figures are not to scale, and are not in proportion,for purposes of clarity. In operation, a pulsed magnetic force F,associated with the magnetic field generated by the welding inductioncoil, is applied to the welding portion 19 of the vessel's body 11 (seeFIG. 2A). According to this embodiment, the welding portion 19 islocated near the open end 12 of the vessel's body 11. However, it shouldbe understood that the location of the vessel's welding portion 19 isnot limited to any part of the vessel's body 11 along its length.

The process of welding the vessel 10 for sealing thereof includesenergizing the welding induction coil 18 to produce the pulsed magneticforce F for bending the vessel's welding portion 19 in a radially inwarddirection around the cover's welding part 14. The welding starts at themoment when an edge 20 of the welding portion 19 contacts the surface 17of the cover's welding part 14 (see FIG. 2B). During the welding, thefront line 21, defining the welding zone WZ, moves tangentially towardsthe brim part 15 (see FIG. 2C), thereby sealing the vessel (see FIG.2D).

It should be understood that in order to provide the welding of thevessel's body and the cover owing to the mutual diffusion of the atoms,the pulsed magnetic force F should have a predetermined value. Morespecifically, the pulsed magnetic force F must have such a value so thatthe vessel's welding portion 19, during its movement in the gap 16towards the surface 17 of the cover's welding part 14, could attain aspeed sufficient for welding the vessel's body to the cover. Forexample, the applicants found that the welding can be established whenan effective speed value of the vessel's welding portion 19 at theimpact is in the range of 250 m/sec-500 m/sec and the apparenttangential speed V_(t) of the front line 21 is in the range of 1000m/sec-2500 m/sec.

FIGS. 3A and 3B illustrate exemplary images obtained from theexamination under an optic microscope (magnification: ×100) of across-section of an etched interface of the joint between the vessel'swelding portion 19 and the cover's welding part 14 made of two similarmetals, such as low carbon steel and aluminum, respectively. FIG. 3Ashows a typical flat shear-like welded interface, while FIG. 3B shows atypical wavy interface. The flat shear-like welded interface can beobtained when the angle between the vessel's welding portion 19 and thecover's welding part 14 at the impact is relatively small, while thewavy interface is obtained when the impact angle is relatively large. Itshould be noted that the magnitude of the angle when the flat shear-likewelded interface changes to the wavy interface depends on the impactspeed and type of material. As can be appreciated by a person skilled inthe art, such an image is a typical picture when a joint is obtained bya pulsed magnetic welding process.

Referring to FIG. 4A and FIG. 4B, an exploded view and a cross-sectionalview of the vessel 10 before a welding process are illustrated,correspondingly, according to another embodiment of the invention. Thisembodiment distinguishes from that shown above in FIGS. 1A and 4B by thefact that the cover 13 here includes openings (one or more). Inparticular, two such openings indicated by a reference numeral 43 areshown in FIG. 4A and FIG. 4B. For example, when the vessel 10 is used asa container, the openings 43 can be required for inserting inlet andoutlet pipes therein.

In this case, when the width of the metal material between the innersurface 44 of the openings 43 and the surface 17 of the cover's weldingpart 14 is small and/or the strength of the material of the cover issmall, the pulsed magnetic force, applied for sealing the vessel asdescribed above, can be high enough in order to cause a collapse of thecover's welding part 14 and to deform the openings 43. In order to avoidthis detrimental phenomenon, a technological plug 41 can be utilizedtogether with the cover 13. The technological plug 41 has one or morepins 42 (two such pins 42 are shown in FIGS. 4A and 4B) configured forinserting them into the openings 43 of the cover 13 and holding thereinduring the energizing of the welding induction coil 18. After theenergizing step, the technological plug 41 can be detached from thesealed vessel. Preferably, the dimension of the pins is such that theycould fill the space of the openings, thereby providing reinforcement tothe cover 13. The pins 42 are made of a material as hard as the materialof the cover 13 or even harder than the material of the cover, e.g.,hardened steel.

It should be noted that in accordance with yet an embodiment of theinvention, when the technological plug 41 is utilized for preventingdeformation of the openings 43, the cover 13 can be without the brimpart 15. In such a case, preferably, the diameter of the plug 41conforms to the inner diameter of the vessel's body 11, thereby holdingthe plug together with the cover 13 within the vessel's body 11. Afterthe sealing process, the plug 41 is detached from the vessel's body 11.

Referring to FIG. 5 a cross-sectional view of the vessel 10 before awelding process is illustrated, according to a further embodiment of theinvention. This embodiment distinguishes from that described in FIGS. 1Aand 1B by the fact that the vessel's body 11 is expanded at the open end12 before the welding process, thereby forming an expanded zone A. Adiameter D_(A) of the vessel's body 11 at the expanded zone A has avalue larger than that of the diameter D_(V) of the vessel's body 11 atits remaining portion. The expanded zone A is provided for the betterholding of the cover 13 within the vessel's body 11. Thus, before thewelding process, according to this embodiment, a value of the diameterD_(CB) of the cover brim part 15 should be about the value of thediameter of the expanded zone A (i.e., D_(CB)≈D_(A)), while the diameterD_(CW) of the cover welding part 14 has to comply with the followinginequality: D_(V)<D_(CW)<D_(A).

Although no openings are shown in FIG. 5 in the cover 13, it can beclear to a versed person that when required, the cover can have one ormore openings. In such a case, the technological plug (41 in FIG. 4A)can be used in order to protect the cover from deformation during thewelding process.

Referring to FIG. 6, a cross-sectional view of the vessel 10 before awelding process is illustrated, according to yet another embodiment ofthe invention. This embodiment distinguishes from that described inFIGS. 1A and 1B by the fact that the vessel's body 11 has an undulatedzone B near the open end 12. The undulated zone B is formed on thevessel's body 11 before the welding process and begins at a distanceequal to the size of the cover welding part 14. The purpose of theundulated zone B is to provide better holding of the cover 13 within thevessel's body 11. Hence, a diameter DB of the undulated zone B has avalue smaller than the diameter D_(V) at the remaining portion of thevessel (i.e., DB<Dv). According to this embodiment of the invention, thevalue of the diameter D_(CB) of the cover brim part 15 should be aboutthe value of the diameter of the vessel's body 11 (i.e., D_(CB)≈D_(V)),while the diameter D_(CW) of the cover's welding part 14 has to complywith the following inequality: D_(B)<D_(CW)<D_(V).

Referring to FIGS. 7A-7C, cross-sectional views of the vessel 10 beforea welding process are illustrated, according to a still furtherembodiments of the invention. These embodiments distinguish from thosedescribed above in the fact that an insulated cylinder 71 is put on thevessel's body 11 for a further reinforcement of the vessel's body 11during the welding. Thus, preferably, the inner diameter of theinsulated cylinder 71 is equal to the outer diameter of the vessel'sbody 11.

Referring to FIG. 8A and FIG. 8B, a prospective view and across-sectional view of the welding induction coil 18 are illustrated,correspondingly, according to an embodiment of the invention. Thewelding induction coil 18 includes a one-turn coil 81 having a canal 82formed into the coil's body for providing a passage of cooling liquidstherethrough. For example, the canal 82 can be drilled duringfabrication of the coil. Two inlets 83 and 84 communicating with thecanal 82 can be used for input and output of liquid, (e.g. water)passing through the coil 18 for cooling thereof during the weldingprocess. Three other technical inlets 85 created in the coil's bodyduring the drilling of the canal 82 are closed by plugs 86, in order toavoid the leakage of the cooling liquid. The inlets 83 and 84 areconnected to a liquid supply line (not shown). When required, the liquidsupply line can be equipped with a liquid pump. When required, theliquid supply line can pass through a cooling system. The cooling systemis known per se, and can be of any conventional kind, e.g., a radiator.

The welding induction coil 18 includes two electrodes I and O coupled toan electric power supply source. For example, the power supply sourcedescribed in U.S. Pat. No. 5,824,998 to Assignee of this application andincorporated herein by reference can be suitable for the purpose of theinvention.

In operation, the vessel's body 11 can be placed into a working zone 89of the welding induction coil 18, preferably, at a distance of about 1-3mm from an inner surface 90 of the one-turn coil 81. The providing andholding of the vessel's body 11 within the welding induction coil 18 canbe done by any appropriate known means. For example, the vessel's bodycan be driven to the welding zone of the working induction coil by meansof a pneumatic cylinder (not shown) or by a hydraulic cylinder (notshown). The working voltage suitable for the purpose of the invention isin the range of about 3 kV to 25 kV. This voltage can provide a pulsedelectric current across the one-turn coil 81 having the amplitude ofabout 10 kA to 1000 kA.

As such, those skilled in the art to which the present inventionpertains, can appreciate that while the present invention has beendescribed in terms of preferred embodiments, the concept upon which thisdisclosure is based may readily be utilized as a basis for the designingof other structures, systems and processes for carrying out the severalpurposes of the present invention.

It is apparent that although the examples of the vessel of the presentinvention were shown for the vessel body portion having a circularcross-section, the sealing method of the present invention can beapplied, mutatis mutandis, for the sealing of a vessel having anarbitrary cross-sectional shape.

It should be appreciated that the method described above can be used forsealing a pipe from two open sides. The pipe includes a vessel's bodyhaving two open ends.

Although an example of the welding induction coil 18 having one-turncoil 81 is described above, it should be apparent that the workinginduction coil can also be a multi-turn coil equipped with afield-shaper.

Moreover, any reference to a specific implementation in terms of usageof the induction coil is shown by way of a non-limiting example.

Also, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of description and should not beregarded as limiting.

In the process claims that follow, alphabetic characters used todesignate claim steps are provided for convenience only and do not implyany particular order of performing the steps.

It is important, therefore, that the scope of the invention is notconstrued as being limited by the illustrative embodiments set forthherein. Other variations are possible within the scope of the presentinvention as defined in the appended claims and their equivalents.

1. A method of sealing a vessel, comprising: (a) providing a vessel'sbody having at least one an open end; (b) providing a cover having awelding part, where said welding part has a diameter less than the innerdiameter of the vessel's body; (c) placing the cover within said atleast one an open end of the vessel's body, thereby an air gap is formedbetween said vessel's body and the welding part of said cover; (d)providing a welding induction coil around said vessel's body at theplace where the welding part of the cover is located; and (e) energizingsaid welding induction coil to generate a pulsed magnetic forcesufficient to cause bending a portion of the vessel's body in a radiallyinward direction around the cover in said air gap, wherein said pulsedmagnetic force has such a value so that (i) said portion of the vessel'sbody during its movement towards the cover's welding part attains at theimpact a speed value in the inward direction in the range of about 250m/sec to 500 m/sec and (ii) a contact front line attains at the impact atangential speed value in the range of about 1000 m/sec to 2500 m/sec,thereby welding said vessel's body and the cover to each other.
 2. Themethod of claim 1 comprising expanding the vessel's body at the open endbefore said placing of the cover within said open end of the vessel'sbody, thereby providing enhanced holding the cover within the vessel'sbody.
 3. The method of claim 1 comprising forming an undulated zone onthe vessel's body before said placing of the cover within the open endof the vessel's body, said undulated zone begins at a distance equal tothe size of the cover's welding part, thereby providing enhanced holdingthe cover within the vessel's body.
 4. The method of claim 1 whereinsaid cover includes at least one opening suitable for inserting a pipetherein.
 5. The method of claim 4 comprising: providing a technologicalplug having at least one pin conforming with said at least one opening;and inserting the technological plug into said at least one opening ofthe cover before the energizing of the coil, thereby.
 6. The method ofclaim 5 wherein pins are made of a material as hard as the material ofthe cover.
 7. The method of claim 5 wherein pins are made of a materialharder than the material of the cover.
 8. The method of claim 7 whereinpins are made of hardened steel.
 9. The method of claim 1 wherein saidvessel's body and said cover are made of the same material.
 10. Themethod of claim 1 wherein said vessel's body and said cover are made ofdifferent materials.
 11. The method of claim 1 wherein said vessel'sbody and said cover are made of a material selected from aluminum, lowcarbon steel, brass, copper and their alloys.
 12. The method of claim 1comprising putting on an insulated cylinder on the vessels body duringthe energizing said welding induction coil.
 13. A sealed vesselcomprising: a vessel's body, where said vessel's body had at least oneopen end before the vessel was sealed; a cover having a welding part,where said welding part has a diameter less than the inner diameter ofthe vessel's body, thereby an air gap was provided between said vessel'sbody and the welding part of said cover placed within the said at leastone open end of the vessel's body before the vessel was sealed, whereinsaid cover being welded to the vessel's body by a pulsed magnetic forcecausing bending a portion of the vessel's body in a radially inwarddirection around the cover in said air gap, said pulsed magnetic forcehas such a value so that (i) said portion of the vessel's body duringits movement towards the cover's welding part attains at the impact aspeed value in the inward direction in the range of about 250 m/sec to500 m/sec and (ii) a contact front line attains at the impact atangential speed value in the range of about 1000 m/sec to 2500 m/sec,thereby providing mutual diffusion of atoms of the vessels body and thecover at their impact.
 14. The sealed vessel of claim 13 wherein saidcover further includes a brim part, where a value of a diameter of thecover at the brim part is about the value of an inner diameter of thevessel's body, thereby to provide holding the cover within the vessel'sbody before the vessel have been sealed.
 15. The sealed vessel of claim13 wherein said cover includes at least one opening suitable forinserting a pipe therein.
 16. The sealed vessel of claim 13 wherein aportion of the vessel's body at the open end is expanded.
 17. The sealedvessel of claim 13 wherein the vessel's body is undulated at thedistance equal to the size of the cover welding part from the open end.18. The sealed vessel of claim 13 wherein said vessel's body and saidcover are made of the same material.
 19. The sealed vessel of claim 13wherein said vessel's body and said cover are made of differentmaterials.
 20. The sealed vessel of claim 13 wherein said vessel's bodyand said cover are made of a material selected from aluminum, low carbonsteel, brass, copper and their alloys.
 21. A welding induction coilcomprising at least a one-turn coil having two electrodes configured forapplying pulsed high voltage thereacross, wherein said welding inductioncoil is configured for use with an apparatus for sealing a vesselincluding: a vessel's body having at least one open end, and a coverhaving a welding part, where said welding part has a diameter less thanthe inner diameter of the vessel's body, thereby providing an air gapbetween said vessel's body and the welding part of said cover when thecover is placed within said at least one open end of the vessel's body;wherein said welding induction coil is configured for and operable togenerate a pulsed magnetic force causing bending a portion of thevessel's body, placed within a working zone of said welding inductioncoil, in a radially inward direction around the cover in said air gap,said pulsed magnetic force has such a value so that (i) said portion ofthe vessel's body during its movement towards the cover's welding partattains at the impact a speed value in the inward direction in the rangeof about 250 m/sec to 500 m/sec and (ii) a contact front line attains atthe impact a tangential speed value in the range of about 1000 m/sec to2500 m/sec, and thereby to weld said cover to the vessel's body.
 22. Thewelding induction coil of claim 21 wherein a canal is formed into a bodyof the coil for providing a passage of cooling liquid therethrough. 23.The welding induction coil of claim 22 wherein said liquid is water. 24.The welding induction coil of claim 21 wherein said pulsed high voltageis in the range of about 3 kV to 10 kV.
 25. (canceled)